A conventional speaker is structured as shown in FIG. 17 and FIG. 18. That is, a magnetic circuit forming a narrow annular magnetic gap 12 between a ring-shaped upper plate 2 and center pole part of a lower plate 3 is composed of a permanent magnet 1 and magnetic material, and a frame 10 holding a diaphragm 8 is fixed on the upper surface of the magnetic circuit. A voice coil 4 for driving a diaphragm is placed in the magnetic gap, and it is supported by a damper 5 so as not to contact with the circumference. A lead wire 6 of the voice coil is a flexible wire so as to withstand repetitive flexures by vibration of the voice coil, and it is connected to an electric connection terminal 7 fixed on the frame 10 as shown in FIG. 17. This connection is called direct connection.
By indirect connection, on the other hand, the end of the voice coil is drawn out onto the upper surface of the diaphragm as shown in FIG. 18, and is connected to the flexible wire 6 of which one end is fixed to the diaphragm 8 on the upper surface of the diaphragm.
The lead wire connection in the conventional voice coil involved the following problems.
(1) In the indirect connection shown in FIG. 18, it requires the skill of passing the end of the flexible wire 6 into the hole in the electric connection terminal 7 and mounting the diaphragm 8 on the frame at the same time. The flexible wire 6 is connected by soldering to the electric connection terminal 7 with a certain sag so as not to interfere the vibration of the voice coil. The speaker is assembled with the frame 10 directed upward, but this soldering connection only is done with the frame 10 set downward, from the outside of the frame, and therefore this process is not preferable for automation of the manufacture. PA0 (2) In the direct connection in FIG. 17, the vibration of the voice coil 4 is directly transmitted to the flexible wire 6. When this vibration is transmitted to the solder connection part of the electric connection terminal 7, the flexible wire 6 may be broken at this point, and therefore solder connection of the electric terminal 7 and flexible wire 6 is down from the outside of the frame with the frame 10 set downward. This process is, as mentioned above, not favorable for automation of the manufacture. Besides, so as not to interfere the vibration of the voice coil, the flexible wire 6 is connected by soldering to the electric terminal 7 with a certain sag, and the sag is manually formed into a specific shape so that the sag may not contact with the diaphragm 8 and the damper 5. PA0 (3) The flexible wire 6 of direct connection is longer than that of indirect connection, and therefore the mass is greater and the treble characteristic of the speaker is poor. Besides, the long flexible wire 6 is likely to vibrate at large amplitude known as rope skipping phenomenon. Once rope skipping occurs, the flexible wire 6 contacts with the diaphragm 8 or damper 5 to cause unusual sound, and fatigue due to flexure is accelerated to lead to wire breakage in a short time. If the flexible wire 6 is increased in thickness and heightened in rigidity in order to suppress rope skipping, the mass increases, and the treble characteristic of the speaker is further worsened. If the flexible wire 6 is much thicker, as shown in FIG. 17, the voice coil bobbin 4a is extended in length for the increment of the thickness of the flexible wire 6, and therefore the attenuation of high frequency vibration propagated to the diaphragm 8 is increased, which also causes deterioration of treble characteristic. In addition, since the height of the speaker is generally limited, the diaphragm 8 is flattened by the portion of increment of the length of the voice coil bobbin 4a, which also causes to worsen the treble characteristic.